England coach Trevor Bayliss has promised a 3-1 Test series win over South Africa won't "paper over the cracks" in his side's fragile top order.

Moeen Ali produced another dramatic finale, the off-spinner taking two wickets in two balls to finish off a 177-run victory in the fourth Test at Old Trafford on Monday for a return of five for 69, after ending England's third Test triumph at The Oval with a hat-trick.

A first home series success over South Africa in 19 years also gave Joe Root a win in his maiden campaign as England captain.

But with just three Tests at home to the West Indies before England begin the defence of the Ashes in Australia, major question remarks remain over several frontline batting positions.

England have tried 11 different players as an opening partner for Alastair Cook since former captain Andrew Strauss retired in 2012.

Durham left-hander Keaton Jennings, the latest in that lengthy list, endured a miserable series against his native South Africa, averaging just 15.87 in eight innings.

Tom Westley made a promising start at No.3 without making a major score, while Dawid Malan's initial impact at No.5 was minimal.

"It's always a good thing that you're winning but we're not papering over the cracks," said Bayliss.

"We know there are some spots which haven't been cemented down and we're still looking for those guys to prove their worth at this level," the Australian added.

Asked if England were now any clearer about the composition of their top order than they had been at the start of the South Africa series, Bayliss replied: "To be honest,no."

"We've got a selection meeting later this week but I'm not going to speculate who might or might not be in the team.

Obviously there's a few spots that will be discussed." 

Root, who along with Cook is the only player in the England top five assured of their place, was left to reflect on a first series as skipper which included a huge 340-run defeat in the second Test at Trent Bridge.

"It's been very enjoyable the majority of the time," he said.

"There was a week that wasn't quite as much fun as the other three, but that is all part and parcel of being a captain," the Yorkshireman added.

"I learnt a lot throughout. It's the start of something."